Contains byte counts for the request handling.
The body bytes count includes transmission overhead (ie: chunked encoding).
ESI sub-requests show the body bytes this ESI fragment including any subfragments contributed to the top level request.
The format is:

Time stamps are issued by Varnish on certain events, and show the absolute time of the event, the time spent since the start of the work unit, and the time spent since the last timestamp was logged. See the TIMESTAMPS section below for information about the individual time stamps.

Timestamps are inserted in the log on completing certain events during
the worker thread's task handling. The timestamps has a label showing
which event was completed. The reported fields show the absolute time
of the event, the time spent since the start of the task and the time
spent since the last timestamp was logged.

The timestamps logged automatically by Varnish are inserted after
completing events that are expected to have delays (e.g. network IO or
spending time on a waitinglist). Timestamps can also be inserted from
VCL using the std.timestamp() method. If one is doing time consuming
tasks in the VCL configuration, it's a good idea to log a timestamp
after completing that task. This keeps the timing information in
subsequent timestamps from including the time spent on the VCL event.